There have been numerous attempts at improving the moldability, surface lubricity, release properties, and water repellency, of thermoplastic resins by blending therein a polyorganosiloxane, for example, dimethylpolysiloxane. Unfortunately, polyorganosiloxane bleed from the surface occurs both during and after molding operations on the thermoplastic resin compositions afforded by these methods, and this causes such problems as a decline in surface lubricity and a reduced mechanical strength. This polyorganosiloxane bleed also causes other problems, such as contamination of the surrounding equipment.
Chemical reaction between the thermoplastic resin and polyorganosiloxane has been pursued in order to deal with these problems. For example, polypropylene-type resin and polyorganosiloxane have been reacted in the presence of a radical-generating catalyst (graft reaction) in order to induce chemical bonding between the two (refer, for example, to Japanese Patent Publication Number Sho 52-36898 and Japanese Patent Application Laid Open Number Hei 6-16824). In these methods, however, the radical reaction between the polypropylene-type resin and the vinyl-functional polyorganosiloxane develops locally, which causes a poor dispersibility of the polyorganosiloxane in the polypropylene-type resin. This results in such problems as, inter alia, providing compositions having poor mechanical strength.